Deep clone utility recommendation

java clone
Juraj picture Juraj · Mar 20, 2009 · Viewed 81.1k times · Source

Is there any utility for deep cloning for java collections:

  • Arrays
  • Lists
  • Maps

NOTE: prefer some solution without usage of serialization, but with use of Object.clone() method. I can be sure that my custom object will implement clone() method and will use only java-standard classes that are cloneable...

Answer

Cojones picture Cojones · Aug 6, 2009

I think the previous green answer was bad , why you might ask?

  • It adds a lot of code
  • It requires you to list all fields to be copied and do this
  • This will not work for Lists when using clone() (This is what clone() for HashMap says: Returns a shallow copy of this HashMap instance: the keys and valuesthemselves are not cloned.) so you end up doing it manually (this makes me cry)

Oh and by the way serialization is also bad, you might have to add Serializable all over the place (this also makes me cry).

So what is the solution:

Java Deep-Cloning library The cloning library is a small, open source (apache licence) java library which deep-clones objects. The objects don't have to implement the Cloneable interface. Effectivelly, this library can clone ANY java objects. It can be used i.e. in cache implementations if you don't want the cached object to be modified or whenever you want to create a deep copy of objects. 

Cloner cloner=new Cloner();
XX clone = cloner.deepClone(someObjectOfTypeXX);

Check it out at https://github.com/kostaskougios/cloning

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